Astacin-like metalloproteases are a gene family of toxins present in the venom of different species of the brown spider (genus Loxosceles)

ABSTRACT

Brown spiders have a worldwide distribution, and their venom has a complex composition containingmany different molecules. Herein, we report the existence of a family of astacin-like metalloprotease toxins in Loxosceles intermedia venom, as well as in the venom of different species of Loxosceles. Using a cDNA library from the L. intermedia venom gland, we cloned two novel cDNAs encoding astacin-like metalloprotease toxins, LALP2 and LALP3. Using an anti-serum against the previously described astacinlike toxin in L. intermedia venom (LALP1), we detected the presence of immunologically-related toxins inthe venoms of L. intermedia, Loxosceles laeta, and Loxosceles gaucho. Zymographic experiments showedgelatinolytic activity of crude venoms of L. intermedia, L. laeta, and L. gaucho (which could be inhibited by the divalent metal chelator 1,10-phenanthroline) at electrophoretic mobilities identical to those reported for immunological cross-reactivity. Moreover, mRNAs extracted from L. laeta and L. gaucho venom glands were screened for astacin-like metalloproteases, and cDNAs obtained using LALP1-specific primers weresequenced, and their deduced amino acid sequences confirmed they were members of the astacin familywith the family signatures(HEXXHXXGXXHE and MXY), LALP4 and LALP5, respectively. Sequencecomparison of deduced amino acid sequences revealed that LALP2, LALP3, LALP4, and LALP5 are relatedto the astacin family. This study identified the existence of gene family of astacin-like toxins in the venoms of brown spiders and raises the possibility that these molecules are involved in the deleterious effects triggered by the venom.